There are known the following so-called single-site catalysts, which are used for producing an olefin polymer such as polypropylene and polyethylene:
(1) a catalyst obtained by contacting a catalyst component, which comprises a metallocene complex such as a metallocene complex and a half-metallocene complex, with a co-catalyst component for activation such as an aluminoxane and tri(n-butyl)ammonium tetraxis(pentafluorophenyl)borate (JP 58-19309A, corresponding to U.S. Pat. No. 4,542,199, and JP 1-502036W, corresponding to EP 277004A); and
(2) a catalyst obtained by contacting with one other a metallocene complex, triisobutylaluminum, and cobalt hexadecafluorophthalocyanine as a co-catalyst component for activation (JP 2001-247611A, corresponding to EP 1113025A).